In Vitro Evaluation of Photoactivated Rose Bengal for Growth Inhibition of Fungi Isolated From Keratitis.

Purpose: The aim of this study was to evaluate the activity of photoactivated 0.1% rose bengal (RB) for in vitro growth inhibition of the most prevalent fungi isolates in infectious keratitis.

Methods: Eight corneal clinical isolates were included in the experiments: Fusarium solani complex, Purpureocillium lilacinum, Candida albicans, Candida parapsilosis complex, Exophiala oligosperma, Scedosporium apiospermum complex, Aspergillus niger complex, and Curvularia geniculata. Microorganisms, previously identified by phenotypical methods, were grown and incubated at specific conditions and prepared in suspension for concentration adjustments. The following groups were evaluated in triplicate: group I, no treatment; group II, treated with RB and exposed to the dark for 30 minutes; group III, exposed to green-light light-emitting diode 7.2 mW for 30 minutes (photodynamic therapy [PDT]); and group IV, treated with RB and PDT (RB-PDT). The final work concentration was 104 cells per mL. The RB-PDT was combined with Amphotericin B (AmphoB) to target isolates that were not inhibited by RB-PDT alone. Plates were incubated at specific conditions and photographed after growth for pixel analyses.

Results: The growth was inhibited after RB-PDT for F. solani complex, P. lilacinum, C. albicans, C. parapsilosis complex, and E. oligosperma, and not inhibited for S. apiospermum complex, A. niger complex, and C. geniculata, even though combining RB-PDT with AmphoB.

Conclusions: RB-PDT presented good activity against five of the tested microorganisms. For the first time, we demonstrated that RB-PDT could inhibit growth of P. lilacinum, C. parapsilosis complex, E. oligosperma, and not inhibit S. apiospermum, A. niger complex, and C. geniculata, even when combined with AmphoB.